Rotary kiln chain



United States Patent inventor Appl. No.

Filed Patented Assignee Frank J. Boron Elyria, Ohio Sept. 3, 1968 Dec.1, 1970 Abex Corporation New York, New York a corporation of DelawareROTARY KILN CHAIN 14 Claims, 5 Drawing Figs.

US. Cl.

Int. Cl. Field of Search 263/33; 34/ M2 F27b 7/00 263/33,

[56] References Cited UNITED STATES PATENTS l,9l0,873 5/l933 Zahn263/33(C)UX 3,442,497 5/1969 Gantz 263/33(C)UX Primary Examiner-John J.Camby Attorney-Kinzer, Born and Zickert ABSTRACT: Rotary kiln chain foruse as a heat transfer element in a rotary kiln used in the manufactureof cement, and like products, including connected circular links formedwith a uniform cross-sectional shape that is substantially greater indimension in one of the axial or radial directions than the other of theaxial or radial directions, and provided with inner engaging surfaceshaving a form that minimizes material buildup to provide more efficientheat transfer action.

Patented Dec. 1, 1970 3,544,092

Shoot 1 of 2 l NTOR FRANK BORON A TORNEYS Patented Dec. 1, 1970 v 13,544,092

' Sadat o! 2 INVENTOR FRANK J. BORON BY I AT ORNEYS ROTARY KILN CHAINThis invention relates in general to a rotary kiln, and moreparticularly to chain employed as a heat transfer means in a rotarykiln, and still more particularly to rotary kiln chain hav ing across-sectional shape that minimizes material buildup and maintainscontinued, efficient heat transfer capability.

The chain of the present invention is employed in rotary kilns used inthe manufacture of cement and like products, and for the purpose .oftransferring heat to the material being treated. For example, a wet, rawmaterial may be fed into the inlet end of a rotary kiln that is rotatedslowly about its axis, and which is disposed at a slight inclinedownwardly toward the delivery end. The chain is suspended within thekiln in any desired manner, and heated gases are directed into thedelivery end of the kiln to transfer heat to the chain, which, in turn,during rotation'of the kiln, comes into contact with the wet, rawmaterial and transfers heat to the material.

Many different shapes of chain links have heretofore been used as heattransfer elements in rotary kilns. For example, one such form is foundin U.S. Letters Pat. No. 3,281,134, granted Oct. 25, 1966, wherein thecross-sectional shape of the link is such that the axial width isgreater than the radial width. This shape is important and advantageousover the conventional rod or wire stock of comparable size, because ofthe reduction in weight willstill maintaining nearly the same heattransfer surface area. Weight reduction isimportant from the standpointof kiln construction and the reduction of power needed to operate thekiln. Thus, it is desirable to reduce weight without materially reducingthe exterior heat transfer area of the chain links. Moreover, the innerengaging surface of each link is somewhat flat and is formed to providenearly complete contact along its axial dimension with another link forthe stated purpose being to minimize wear caused by interengagement ofadjacent links. This structure has been objectionable in thatundesirable material buildup is experienced, and which is detrimental toefficient kiln operation. The buildup is such that the links becomepartially or fully plugged, thereby impeding gas flow through the chainsection, and ultimately causing production problems. Material buildupalso reduced the heat transfer capability of the links due to theinsulating properties oflinks covered with material.

The chain of the present invention obviates the above difficulties byproviding a structure that eliminates or substantially eliminatesmaterial buildup by enabling better cleaning action between links,thereby maintaining effective and efficient gas flow through the chainsection. Further, by maintaining the links substantially clean, becauseof the more efficient cleaning action established, the heat transferproperties of the links are utilized to their fullest.

The chain of the present invention includes connected links, whereineach link is provided with a uniform cross-sectional shape throughoutthe circumference thereof. One of the axial or radial thicknesses of thelink cross-sectional shape is substantially greater than the other ofthe axial or radial thicknesses. More efficient cleaning action isobtained by forming the inner surface of the link to define minimalengaging contact with another link, thereby enhancing self-cleaning asthe links move relative each other minimizing material buildup betweenlinks. In one embodiment, the axial thickness is greater than the radialthickness and the inner surface is V- shaped, so that a relatively knifeedge contact is established between adjacent links. In anotherembodiment, the radial thickness of the link cross-sectional shape issubstantially greater than the axial thickness, thereby automaticallyminimizing the relativeengaging contact between links. In this latterembodiment, it has also been found that the pull strength is materiallyincreased.

Accordingly, it is an object of the present invention to provide animproved rotary kiln chain'that enhancesself-cleaning and eliminates orsubstantially eliminates material buildup between links.

Another object of this invention is in the provision'of chain for rotarykiln having a more efficient cleaning action between links, therebymaintaining the heat transfer ability throughout 7 its life,and'throughout its operation in a kiln, and to enable efficient gas flowthrough the chain section.

A further object of this invention resides in the provision of rotarykiln chain having the inner, engaging surface formed to facilitatecleaning action and to provide minimal, engaging contact between links.

Other objects, features and advantages of the invention will be apparentfrom the following detailed disclosure, taken in conjunction with theaccompanying sheets of drawings, wherein like reference numerals referto like parts, in which:

FIG. 1 is a vertical, sectional view taken through a rotary kiln andillustrating one section of chain suspended within the kiln;

FIG. 2 is a plan view of several links of chain constructed inaccordance with the present invention;

FIG. 3 is a view of several links of chain, illustrating some of thelinks in section and one link in plant to illustrate the interactionbetween links;

FIG. 4 is a plan view of several links of chain illustratingmodifications of the invention; and

FIG. 5 is a view of the chain of FIG. 4, illustrating some links insection and one link in plan to show the interconnection and engagementof the links.

An exemplary kiln within which the kiln chain of the present inventionwould be employed as a heat-exchanging element is illustrated in FIG. 1,and is generally indicated by the numeral 10. This kiln is of the rotarytype that would have a large diameter and an extremely long length,depending upon the particular installation. The kiln would be suitablysupported for rotary movement about its axis, and be powered to rotateat a slow speed. Moreover, the kiln would be inclined downwardly fromthe inlet end to the discharge end. The

material to. be treated would be introduced at the inlet end, I

- treated. And the chain sections may be secured in any other fashion,such as solely from one end of the section.

The present invention relates primarily to the cross-sectional shape ofchain which enhances the efficiency during its use in a kiln, so that itcan maintain a high and desired production output, as well as enhancingits life to reduce the chain costs involved in a kiln. While theembodiments illustrated show links of particular construction, it shouldbe appreciated that the present invention could also be applied to linksof other configurations.

It has been accepted in the industry that circular link design is mostpreferable on the basis that it is self-cleaning, and wears evenly,because it can rotate, and has the least tendency to entangle. However,some circular link chain, such as that shown in the aforesaid U.S. Pat.No. 3,281,134 has been objectionable because of material buildup, whichinterferes with the efficiency of kiln operation. In particular,material buildup can result in plugged chain that interferes with thheated gas flowthrough the chain section, thereby causing productionproblems. For example, interfering of gas flow through any section mightresult in overheating of chain in another section, which would have adetrimental effect on chain life. Further, material buildup interfereswith the heat transferability of the chain inasmuch as it effectivelyapplies a heat insulating layer on the chain. Such would reduceproduction of a kiln. The contact between links of the chain of theaforesaid patent is substantial and complete relative to the axial widthof the links. The material buildup problem has been overcome in thepresent invention by providing chain having minimum interengagingcontact.

In the first embodiment of the present invention, FIGS. 2 and 3,circular links 12 are sized so that with respect to the cross-sectionalshape the axial width of each link is substantially greater than theradial width, just as the chain link in the aforesaid patent. The innersurface of each link is formed to produce point or knife edge engagementbetween successive links, which engagement provides a cleaning actionthat substantially if not completely eliminates material buildup betweenlinks. In this respect, the cross-sectional shape of the inner surfaceof each link is substantially V-shaped and includes fiat surfaces 13 and14, which define at the junction a relatively sharp or knife edge 15,that is located along a central plane extending through each link. Theflat surfaces are continuous relative to the circumferential characterof each link, and, therefore, annular. From this central plane, andconsidering the cross-sectional shape, the cross section is symmetrical.The outer surface 16 is arcuate and smooth, and formed by an arc havinga radius about equal to the radius of the inner diameter of the link.This outer surface is connected at each of its ends by arcuate end faces17 and 18 to the flat faces 13 and 14.

During use in a kiln, the links 12 will change position, as the chaincondition transforms from-slack to tight or suspended condition, so thatbearing contact with an adjacent link will vary along the knife edge 15.As seen in FIG. 3, the knife edge of one link will engage the knife edgeof an adjacent link. This relatively sharp edge contact and the normalmovement of the links relative to each other will produce an effecientcleaning action, so as to substantially, if not completely eliminatematerial buildup on the chain. Buildup will be efficiently eliminatedbetween chain links at the bearing contact engaging faces, and will alsobe eliminated at the outer surfaces of the links by virtue of when thechain goes slack, the inner surfaces of some links will engage the outersurfaces of other links. This efficient cleaning action will, bypreventing material buildup, maintain the chain links open andunplugged, thereby utilizing the gas flow in the chain section.Moreover, the maintaining of the links in substantially clean conditionwill enable substantially complete use of the heat transfer surface onthe links. Overall, the, chain of the present invention will facilitateefficient operation of a kiln,-and enhances chain life.

While the chain of the embodiment of FIGS. 2 and 3 may have any desiredsize and weight, and may be constructed in any desirable manner, it ispreferably cast of an alloy steel having the following approximatedimensions. Each link would have an outside diameter of 45/ 16 inchesand an inside diameter of 3 inches and have a radial width of twenty one-thirty two seconds inch and an axial width of 1 9/32 inches. This wouldproduce a link that would have an estimated weight of 2.12 pounds. Thechain weight per foot would be about 8.48 pounds, while the surface areaper link would equal 34.46 square inches.

Another embodiment of the invention is shown in FIGS. 4 and S that isconstructed to perform the same efficient cleaning action on a chain asthe embodiment of FIGS. 2 and 3. The link of this embodiment isgenerally identified as 12A. Each link 12A is circular and includes aninner surface 20 of arcuate shape for bearing engagement with the innersurfaces of adjacent links defined by a radius that is substantiallysmaller than the inner radius of the link, an outer surface 21 ofarcuate shape and of the same shape as the inner surface 20, and arcuateinterconnecting end faces 22 and 23. The interconnecting end faces 22and 23 are substantially flat and the cross-sectional shape is such thatthe radial width is substantially greater than the axial width.Moreover, the cross-sectional shape is symmetrical in form.

The inner surface 20 is formed so that it defines with an adjacent linkminimal engaging contact as shown in FIG. 5. In this respect, itisoperable just like the embodiment of FIGS. 2 and 3 in that efficientself-cleaning action is obtained by the links during operation in a kilnThe size and weight of the chain of this embodiment maybe according tothe needs of the kiln, but a size and weight that is comparable to thatof the embodiment of FIGS. 2 and 3 will provide substantially the sameweight per link and substantially the same heat transfer surface. Theouter diameter of each link would be 5 6 inches while the inner diameterwould be 3 inches. The axial width of a cross section would be .670inches while the radial width would be about 1 H16 inches. A link ofthis size would have an estimated weight of 2.02 pounds, while a chainwith links of this type would weight about 8.08 pounds per foot. Thesurface area of each link would be about 35.61 square inches.

An added advantage for a chain of this configuration would be to havethe same area and weight with greater strength. The pull strength for achain of this link structure is about five to six times the pullstrength of the chain in FIGS. 2 and 3.

Essentially, the cross-sectional shape of this embodiment is turnedrelative to the cross-sectional shape of the embodiment of FIGS. 2 and3. As in the first embodiment this chain may be made in any suitablemanner, such as by casting from alloy steel.

From the foregoing, it can be appreciated that the chain of the presentinvention will enable efficient and long-life operation of a kiln byminimizing material buildup, while providing maximum heat transfer withminimum weight.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention, but it is understood that this application is to be limitedonly by the scope of the appended claims.

lclaim:

1. Rotary kiln chain comprising, connected links, each link having auniform, cross-sectional shape throughout, said link cross'sectionalshape throughout, said link cross-sectional shape having an axialthickness and a radial thickness as taken relative the link center and amedial plane extending therethrough, one of said thicknesses beingsubstantially greater than the other, and the inner surface of said linkcrosssectional shape being formed to provide substantially single pointand minimal engaging contact with an adjacent link, thereby enhancingthe cleaning action between links and minimizing material buildup.

2. Rotary kiln chain comprising, connected links, each link having auniform'cross-sectiona] shape throughout, said link cross-sectionalshape having an axial thickness and a radial thickness as taken relativethe link center and a medial plane extending therethrough,'said axialthickness being substantially greater than said radial thickness, andthe inner surface of said link cross-sectional shape being formed toprovide minimal engaging contact with an adjacent link thereby enhancingthe cleaning action between links and minimizing material buildup.

3. Rotary kiln chain as defined in claim 2, wherein the inner surface ofeach link is V-shaped to provide substantially knife edge contactbetween links.

4. Rotary kiln chain as defined in claim 3, wherein the links arecircular.

5. Rotary kiln chain as defined in claim 4, wherein the outer surface ofeach link is particircular on a radius substantially equal to the innerradius of each link.

6. Rotary kiln chain as defined in claim 1, wherein the radial thicknessis substantially greater than the axial thickness.

7. Rotary kiln chain as defined in claim 6, wherein the inner surface isparticular.

8. Rotary kiln chain comprising connected, substantially circular linkshaving a uniform cross-sectional shape throughout the circumferencethereof and a dimension in a direction transverse the planes of thelinks substantially greater than the thickness thereof within saidplanes, and the inner bearing surface of said links being formed toprovide substantially point contact therebetween, whereby the bearingcontact substantially eliminates material buildup at the inner surfaces.

9. Rotary kiln chain as defined in claim 8, wherein said inner surfaceif V-shaped to provide a substantial knife bearing surface.

l0. Rotary kiln chain as defined in claim 8, wherein said outer surfaceis particircular on a radius substantially equal to the inner radius ofeach link.

1]. Rotary kiln chain comprising connected substantially circular linkshaving a uniform cross sectional shape through the circumference thereofwith arcuate inner and outer surfaces, said cross-sectional shape havinga dimension in a direction transverse to the planes of the linkssubstantially more narrow than the thickness thereof with in said planesthereof, and the inner surface being formed with a radius substantiallysmaller than the plane radius of the links to define

